Production of Bio-ethanol from Cassava Peels *Olayide R. Adetunji, Pritlove K. Youdeowei & Olalekan O. Kolawole Mechanical Engineering Department, College of Engineering, Federal University of Agriculture, Abeokuta, P.M.B.2240, Abeokuta, Ogun State, NIGERIA *E-mail: adetunjior@funaab.edu.ng ABSTRACT The rising energy requirements and atmospheric contamination by combustion gases and conventional fuel, has opened avenues for new, safe, effective and more accessible energy sources. This study looked at the production of bio-ethanol from cassava peels. Cassava peels were collected from cassava processing sites, prepared by washing to remove sand, dirt, and other impurities that may affect the results, the peels were then sun dried for some days to remove moisture and grinded into cassava flour, the flour was thereafter cooked to slurry to aid enzymatic activity in the laboratory. Aspergillus Niger (A.N) was used for the hydrolysis for seven days, and was aseptically added to the autoclaved samples. The uniform action of enzymes was achieved throughout the sample, also Saccharomyces cerevisiae was used for the fermentation of the hydrolysate for seven days, and this was aseptically added to the hydrolysate after filtration and autoclaving at 121 o C for 15 mins. Distillation of the fermented liquid was carried out immediately after fermentation, 8.5 % of ethanol by volume was produced after distillation from the 20 g sample. The ph was measured at 6.71, the distillation range was between 78-100, the flash point was also obtained as 24 o C.The results showed that cassava peel starches can be readily degraded by A. N. The bio-ethanol produced was comparable with ethanol. Keywords; Bio-ethanol, Cassava peels, Renewable energy, Enzymes, Fermentation, Distillation 1.0 Introduction Increasing energy requirements and atmospheric contamination by combustion gases, has opened avenues for new, safe, effective and more accessible energy sources. People Livelihood diversification would require the understanding of society dynamics in terms of domestic energy consumption as well as investigating possible ways of producing energy from available resources (Amigun et al.,2008). Bioethanol is a microbiological way of converting simple sugar into ethanol and carbondioxide (CO) (Damaso et al
2004).Bioethanol is a principal fuel that can be used as petrol substitute for vehicle (Aro et al 2005). It is a renewable energy source produced mainly by sugar fermentation process, although it can also be manufactured by the chemical process of reacting ethylene with steam (Anuj et al 2007). The main sources of sugar required to produce ethanol come from fuel or energy crops (Kim et al 2005). These crops include maize, cassava and cassava products, wheat crops, waste straw, guinea corn husk, rice husk, millet husk, sawdust and sorghum plant. Ethanol is a high octane fuel and has replaced lead as an octane enhancer in petrol (Oghgren et al 2006). By blending ethanol with gasoline we can also oxygenate the fuel mixture so it burns more completely and reduces pollution emission. Ethanol fuel trends are widely sold in the United State. The national average prices between July 1 and July 15 2014 ranges from Biodiesel (B20) $3.98/gallon, Biodiesel(B99-B100) $4.24/gallon, Electricity $0.21kwh,Natural Gas(CNG) $2.17/GGE, Propane $3.07/gallon, Gasoline $3.70/gallon, Ethanol $3.23/gallon and Diesel $3.91/gallon. The above data shows that ethanol is cheaper than gasoline (petrol) on average and readily available in countries utilizing their energy crops potential like Brazil. Non-food parts of the cassava may play a very significant role in the production of energy since they produce relatively high amounts of biomass, are easily hydrolysable and have a high content of dry matter (Kosugi et al.,2009).the most common blend is 10% ethanol and 90% petrol (E) and vehicle engines require no modification to run on ethanol and vehicle warranties are unaffected also. Ethanol derived from biomass is the only liquid transportation fuels that do not contribute to the greenhouse gas effect (Adelekan, 2010, Nuwamanya et al.2010, Anuj et al 2007). Ethanol has been produced in batch fermentation with fungi strains such as Aspergillus niger, Mucor mucedo, Saccharomyces cerevisiae that cannot tolerate high concentration of ethanol (Ledward et al 2003.Oyeleke et al 2008, Seema et al., 2007).Biofuels can be produced by many different types of substrates. Among these, cassava (Manihot esculenta Crantz), a plant with high starch content, is considered a cheap, abundant and renewable resource for production of fermentable glucose syrups and dextrins. Moreover, it is easily produced in tropical and sub-tropical zones, mainly in Asia, South-America and South-Africa. The technological availability and awareness of Africans especially local farmers to the economic potential of utilizing cassava waste in bio-ethanol production poses a great problem. The source of enzyme extraction and the conditions of operation of enzymes such as ph, temperature, reaction time, enzyme concentration, viscosity, mixing rates etc. in soluble solutions must be optimized to improve the economic and technological feasibility of the bio-process. This research work therefore examined the Production of Bio-ethanol from Cassava Peels.
2.0. Materials and Methods Four hundred grams (400g) of cassava peels were collected from cassava dump sites and processing areas within Abeokuta. These were asceptically collected in a polythene bag. The organisms used were Aspergillus niger and Saccharomyces cerevisiae, these were collected from micro-biology laboratory, of the federal university of agriculture, Abeokuta, Ogun State, Nigeria. The methods used for Bioethanol production includes; enzyme hydrolysis, fermentation and distillation process. Enzyme hydrolysis involves washing of the cassava peels to remove dirt, dust and other impurities and sundried for three days to remove or extract moisture, and thereafter ground to flour. The flour was cooked to slurry to aid the enzymatic activity. Different quantities of the substrates were weighed inside separate 500 cm 3 conical flasks; two 20 grams in two separate conical flask and another two 50 grams in two other separate conical flasks. One of each set of conical flask acted as control. Sterile distilled water was added to make up to the mark and the flasks were plunged with sterile cotton wool wrapped in aluminium foil to avoid contamination. The mixtures were sterilized in an autoclave at 121 o C for 15 minutes, allowed to cool and sterile distilled water was aseptically added to make up to mark again. Freshly harvested cells of Aspergillus niger was inoculated into a set of 20 grams, and 50 grams of each substrates mixture under aseptic condition, while the other set served as control for the two substrates. The flasks were covered and were then incubated at room temperature (28 o C) for seven days. The flasks were shaken at interval to produce a homogenous solution and even distribution of the organisms in the substrates mixture. The mixtures were separately filtered after seven days using No 1 Whatman filter paper. Supernatant from the hydrolysis process were transferred into another sets of conical flasks correctly labelled, covered, autoclaved at 121 o C for 15 minutes and allowed to cool. Freshly harvested cells of Saccharomyces cerevisiae was added into the set of hydrolysed supernatant (20 g and 50 g) for fermentation process. The flasks were corked using cotton wool, shaken and incubated at room temperature (28 o C ±2 o C) for seven days. The flasks were shaken at intervals to produce a homogenous solution and even distribution of the organisms in the substrates mixture.
The fermented liquid was transferred into round bottom flask and placed on a heating mantle fixed to a distillation column enclosed in running tap water. Another flask was fixed to the other end of distillation column to collect the distillate at 78 o C (standard temperature for ethanol production). This was done for each of the fermented broth. The distillate collected was measured using a measuring cylinder and expressed as quantity of ethanol produced in g/l by multiplying the volume of the distillate by the density of ethanol (0.8033g/cm). The tests carried out to characterize the ethanol produced included; flash point, ph, density and specific gravity, viscosity and distillation range using various techniques and tools. 3.0 Results and Discussion The physical properties of standard ethanol and ethanol produced are compared in the table 1 with the melting and boiling point of both being the same. Table 1 Melting and Boiling points of Ethanol produced Fuel Melting Point C Boiling Point C Standard Ethanol -114.1C 78.5C Ethanol Produced -114.1C 78.5C Table 2 Mineral composition of inoculated and un-inoculated Cassava peel wastes Components Cassava peel media Control Degraded Cassava peel media Inoculated with Aspergillus niger
Crude protein (%) 1.80 11.26 Crude fibre (%) 46.7 30.56 Fat (%) 1.74 5.14 Ash (%) 6.26 4.31 It was observed that the percentage hydrolysis at day one was 12.3%, it then increased steadily to 28.5% at the second day, with a rapid increase of 38.5% observed at the third day. It later increased up to 78% on the fourth day and increased linearly to 82% on the seventh day. Figure 1 Percentage hydrolysis of milled Cassava peels against days of treatment Quantity of ethanol produced The percentage ethanol produced increased linearly with the number of days of treatment. The first day produced 1.21% (lowest) of ethanol followed by thorough shaking, then the second day recorded an amount of 2.42% and it progressively increased to 8.5% for the seventh day (highest) for the 20g sample.meanwhile the percentage ethanol produced for the first day was 2.14% and 15% on the seventh day for the 50g sample.
Percentage Ethanol Table 3 The viscosity and ph test results of the 20 g and 50 g samples. Amount of sample Viscosity(CST) ph Test 20 grams 1.105 6.71 50 grams 1.103 6.71 17.12 14.98 12.84 10.7 8.56 2.14 1.21 4.28 2.42 6.42 3.63 4.84 6.05 7.26 8.47 9.68 No of Days of Treatment 50g Sample 20g Sample Fig 2 Graph of Percentage Ethanol against No of days of Treatment.
Table 4 Distillation range and Flash point of ethanol produced from the 20 g and 50 g amples. Sample weight Initial volume of Distillate(mL) Final volume of Distillate(mL) Distillation Range(C) Flash Point(C) 20grams 120 105 78-100 24 50grams 230 210 78-100 24 Figure 4 The graph of viscosity against temperature. Discussions The melting point and the boiling point of the standard ethanol and ethanol produced are shown in the Table 4.0. Both values for melting and boiling point of the standard ethanol and the ethanol produced are identical.
The Aspergillus niger isolated from Cassava peel wastes successfully hydrolysed the Cassava peel material as was evidenced by an increases in protein content and a decrease in fibre content. The percentage hydrolysis of milled cassava peels as shown in Figure 2 increases from day 1 to day 4 and subsequently stabilize to day 5.Also the reducing sugar concentration in a suspension of sugar milled cassava peels followed the same pattern (Figure 3) as the percentage hydrolysis shown in Figure 2. The rate of growth of cells in suspension of milled cassava peels as shown in Figure 4 increases logarithmically from day 1 to day 4 and later stabilized at day 5. The ethanol production for seven days from cassava peels hydrolysate as shown in Fig 5 reveals that the ethanol production reached 8.5% and 15% at the seventh day while the two set of controls remained relatively the same with percentage alcoholic content rather insignificant. This study showed that cassava waste (peels) was readily degraded by A niger Thus, the successful degradation of Cassava peel by A. niger may be attributed to its amylolytic nature, as over 96% of the starchy component of the peel was transformed to simple reducing sugar during the wet-state fermentation as reported by Adesanya et al.2008. 4.0 Conclusion Based on the fermentation of the hydrolysate with Saccharomyces cerevisiae after seven days resulting in the maximum bio-ethanol production which was at concentrations of (8.5 %) for the 20 g sample and 15% for the 50 g sample respectively, it is an indication that
Saccharomyces cerevisiae was able to synthesize hydrolysate, the followings can be concluded: The hydrolysis of cassava peels by A. niger to yield simple reducing sugars was sufficient to allow S. cerevisiae to produce ethanol by fermentation. The physical properties of the ethanol produced conformed to that of standard one in terms of ph, viscosity, distillation range and flash point. References Adelekan, B.A., 2010. Investigation of ethanol productivity of cassava crop as a sustainable source of biofuel in tropical countries African Journal of Biotechnology Vol. 9(35), pp 5643-5650, 30 August, 2010. Adesanya, O.K., Oluyemi, S., Josiah, R.A., Shittu, L. D., Ofusori, M., Bankole, and Babalola, G., 2008. Ethanol production by Saccharomyces cerevisiae from Cassava Peel Hydrolysate. Internet Journal of Microbiology 5: 1. Amigun, B., Sigamoney, R and von Blottnitz, H., 2008. Commercialisation of biofuel industry in Africa: A review. Renewable and Sustainable Energy Reviews 12 pp 690 711. Anuj, K.C., Ravinder, R., Lakshmi, M.N., Rao, V., and Ravindra, P., 2007. Economic and Environmental impact of Bioethanol Production Technology. Biotechnology and molecularbiology review. 2(1) pp14-32. Armstrong, S.R., 1999. Ethanol Brief Report on its Use in Gasoline. http://www. ethanol.org/pdfs/health_impacts.pdf. Aro, N., Pakula, T., and Pentella, M., 2005. Transcriptional regulation of plant cell wall. Degradation by filamentous fungi. Fems Microbiology revolution, 29 pp 719-739. Damaso, M., Castro, M.R., and Adrade, M.C., 2004. Application of xylanase from Thermomyces lanuginosus for enzymatic hydrolysis of corn cob and sugar cane Baggase. Applied Biochemistry and Biotechnology. 15 pp1003-1012.
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